Scientists define the biosphere
as the narrow layer around
Earth's surface in which life can
In a broader sense; biospheres
are any closed, self-regulating
systems containing ecosystems;
The biosphere is the global sum of
all ecosystems. It can also be called
the zone of life on Earth, a closed
(apart from solar and cosmic
radiation), and self-regulating
The biosphere is located near Earth's surface
because most of the sunlight is available near
Plants need sunlight to produce their food,
and almost every other organism gets its food
from plants and algae.
Most of these algae float at the surface of the
The biosphere extends about 11 km
into the ocean and about 9 km into
the atmosphere, where
insects, bacteria, and pollen grains
have been discovered.
Both the biosphere and environment
influence each other a lot.
Life exists on Earth because of several
Life requires liquid water, temperatures
between 10°C and 40°C, and a source of
The materials that organisms require must
continually be cycled.
Suitable combinations of the things that
organisms need to survive are found only in
The actual thickness of the
biosphere on earth is difficult to
measure. Birds typically fly at
altitudes of 650 to 1,800
meters, and fish that live deep
underwater can be found down
to -8,372 meters
Energy Flow in the Biosphere
The energy used by organisms must be
obtained in the biosphere and must be
constantly cycled for life to continue.
When an organism dies, its body is broken
down and the nutrients in it become available
for use by other organisms.
This cycling of energy allows life on Earth to
continue to exist.
Energy enters the biosphere in the form of
sunlight, which plants use to make their food.
When an animal eats a plant, the energy
stored in the plant is transferred to the
animal. Animals in turn eat other animals.
At each stage in the food chain, some of the
energy is lost to the environment as
heat, which is eventually lost to space.
The biosphere forms a thin crust of
living beings over the surface of our
planet and consists of an immense
variety of organisms out of which
only about 1.5 million species have
been identified and described.
The existence and well being of living
organisms depend on a system of complex
interactions within and in between the
components of environment - the
lithosphere, hydrosphere, atmos-phere and
the biosphere itself.
It is these interactions which satisfy all needs
of all living organisms, such as
shelter, water, oxygen to respire, mates to